services:
  web:
    image: nginx:alpine
    ports:
      - "8080:80"
  db:
    image: postgres:15
    environment:
      POSTGRES_PASSWORD: example

volumes:
  pgdata:
    driver: local

  volumes:
    - ./data:/var/lib/postgresql/data
  

networks:
  app_net:
    driver: bridge

DB_PASSWORD=secure_password

services:
  db:
    environment:
      POSTGRES_PASSWORD: ${DB_PASSWORD}

services:
  app:
    depends_on:
      - db
  db:
    image: postgres

db:
  image: postgres
  healthcheck:
    test: ["CMD-SHELL", "pg_isready -U postgres"]
    interval: 5s
    timeout: 5s
    retries: 10

  app:
    depends_on:
      db:
        condition: service_healthy
  

├── docker-compose.yml
├── docker-compose.override.yml   # Для dev
└── docker-compose.prod.yml       # Для prod

  docker-compose -f docker-compose.yml -f docker-compose.prod.yml up
  

  # docker-compose.override.yml
  services:
    app:
      environment:
        DEBUG: "true"
      volumes:
        - ./src:/app/src
  

version: '3.8'
services:
  app:
    build: ./app
    ports:
      - "8080:8080"
    environment:
      SPRING_DATASOURCE_URL: jdbc:postgresql://db:5432/mydb
      SPRING_DATASOURCE_PASSWORD: ${DB_PASSWORD}
    depends_on:
      db:
        condition: service_healthy
    networks:
      - app_net

  db:
    image: postgres:15
    environment:
      POSTGRES_DB: mydb
      POSTGRES_PASSWORD: ${DB_PASSWORD}
    volumes:
      - pgdata:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 2s
      timeout: 5s
      retries: 15
    networks:
      - app_net

volumes:
  pgdata:

networks:
  app_net:
    driver: bridge

services:
  kafka:
    image: bitnami/kafka:3.5.1
    container_name: kafka
    ports:
      - "9092:9092"
    environment:
      KAFKA_CFG_NODE_ID: 0
      KAFKA_CFG_PROCESS_ROLES: broker,controller
      KAFKA_CFG_LISTENERS: PLAINTEXT://:9092,CONTROLLER://:9093
      KAFKA_CFG_ADVERTISED_LISTENERS: PLAINTEXT://kafka:9092
      KAFKA_CFG_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,CONTROLLER:PLAINTEXT
      KAFKA_CFG_CONTROLLER_LISTENER_NAMES: CONTROLLER
      KAFKA_CFG_INTER_BROKER_LISTENER_NAME: PLAINTEXT
    networks:
      - app_net

  app:
    # ... (Java-сервис из предыдущего примера)
    depends_on:
      - kafka

# application.properties
spring.kafka.bootstrap-servers=kafka:9092
spring.kafka.consumer.group-id=my-group

Properties props = new Properties();
props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "kafka:9092");
props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
KafkaProducer<String, String> producer = new KafkaProducer<>(props);

public class Task080925 {
    public static void main(String[] args) {
        Long a = 100L;
        Long b = 100L;
        Long c = 200L;
        Long d = 200L;
        
        System.out.println((a == b) + " " + (c == d));
    }
}

public interface InterfaceName {
    // Абстрактные методы
    // (с Java 8) default и static методы
}

public interface Drawable {
    void draw();  // Неявно public abstract
}

public class Circle implements Drawable {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    @Override
    public void draw() {
        System.out.println("Рисую круг радиусом " + radius);
    }
}

public class Square implements Drawable {
    private double side;

    public Square(double side) {
        this.side = side;
    }

    @Override
    public void draw() {
        System.out.println("Рисую квадрат со стороной " + side);
    }
}

public class Main {
    public static void main(String[] args) {
        Drawable[] shapes = {new Circle(5.0), new Square(4.0)};
        for (Drawable shape : shapes) {
            shape.draw();  // Вызывает Circle.draw() или Square.draw()
        }
    }
}

Рисую круг радиусом 5.0
Рисую квадрат со стороной 4.0

default returnType methodName(params) {
    // Реализация
}

public interface Drawable {
    void draw();

    default void describe() {
        System.out.println("Это фигура, которую можно нарисовать.");
    }
}

public class Circle implements Drawable {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    @Override
    public void draw() {
        System.out.println("Рисую круг радиусом " + radius);
    }

    @Override
    public void describe() {
        System.out.println("Это круг радиусом " + radius);
    }
}

Вызов circle.describe(): "Это круг радиусом 5.0".
Square использует default: "Это фигура, которую можно нарисовать.".

public interface Drawable {
    void draw();

    default void describe() {
        System.out.println("Это фигура, которую можно нарисовать.");
    }

    static void printInfo() {
        System.out.println("Интерфейс Drawable для рисования фигур.");
    }
}

Drawable.printInfo();  // Вывод: Интерфейс Drawable для рисования фигур.

Нюанс: Circle.printInfo() — ошибка, только Drawable.printInfo().

public class MyClass implements Interface1, Interface2 {
    @Override
    public void method() {
        Interface1.super.method();  // Выбор реализации
    }
}

interface Calculator090925 {
    static int multiply(int a, int b) {
        return a * b;
    }
    
    default int add(int a, int b) {
        return a + b;
    }
}

class Math090925 implements Calculator090925 {}

public class Task090925 {
    public static void main(String[] args) {
        Math090925 math = new Math090925();
        System.out.println(math.add(2, 3));
        System.out.println(Math.multiply(2, 3));
    }
}

  ARG JAVA_VERSION=17
  ENV JAVA_VERSION=${JAVA_VERSION}
  Здесь JAVA_VERSION станет частью образа и будет доступна в runtime.

  docker build --secret id=github,src=./github.token .
  

  RUN --mount=type=secret,id=github \
      git clone https://$(cat /run/secrets/github)@github.com/private/repo.git
  

ARG MAVEN_VERSION=3.8.6
ARG USER_HOME_DIR="/root"
RUN mkdir -p /usr/share/maven && \
    curl -fsSL "https://archive.apache.org/dist/maven/maven-3/${MAVEN_VERSION}/binaries/apache-maven-${MAVEN_VERSION}-bin.tar.gz" \
    | tar -xzC /usr/share/maven --strip-components=1

  docker buildx create --use
  docker buildx build --platform linux/amd64,linux/arm64 -t myapp:latest .
  

docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
    

# Сборка под ARM64 и x86_64
FROM --platform=$BUILDPLATFORM openjdk:17 AS builder
ARG TARGETARCH
RUN echo "Собираем под архитектуру: ${TARGETARCH}"
COPY . .
RUN ./mvnw package -DskipTests

.git
.gitignore
**/target/
**/*.log
**/.idea/
**/.vscode/
docker-compose.yml

jdeps --print-module-deps target/myapp.jar
Вывод: java.base,java.logging,java.xml.  
   

   RUN jlink \
       --add-modules java.base,java.logging,java.xml \
       --output /jlinked \
       --strip-debug \ — удаление отладочной информации.  
       --compress 2 \ — максимальное сжатие (уменьшает размер на 30%).  
       --no-header-files \
       --no-man-pages
   

FROM gcr.io/distroless/java17-debian11
COPY --from=builder /app/target/myapp.jar /app.jar
ENTRYPOINT ["/app.jar"]

# Создаем пользователя с UID 1001
RUN adduser --uid 1001 --disabled-password --gecos "" appuser
USER 1001
COPY --chown=1001:1001 target/myapp.jar /app.jar
ENTRYPOINT ["java", "-jar", "/app.jar"]

    # docker-compose.yml
    app:
      cap_add:
        - NET_BIND_SERVICE
    

  RUN mkdir /app/tmp && chown 1001:1001 /app/tmp
  ENV JAVA_OPTS="-Djava.io.tmpdir=/app/tmp"

   # Stage 1: Сборка
   FROM maven:3.8.6 AS builder
   COPY . .
   RUN mvn package

   # Stage 2: Финальный образ
   FROM openjdk:17-jre-slim
   COPY --from=builder target/myapp.jar /app.jar
   

   RUN apt-get update && \
       apt-get install -y curl && \
       rm -rf /var/lib/apt/lists/*
   

   RUN rm -rf $JAVA_HOME/jmods/java.corba.jmod
   

  docker run -m 512m --cpus=1.5 myapp
  

  environment:
    JAVA_TOOL_OPTIONS: "-XX:MaxRAMPercentage=75.0" //указывает JVM использовать 75% от лимита cgroups.

docker exec myapp cat /sys/fs/cgroup/memory.max
docker exec myapp cat /sys/fs/cgroup/cpu.max

   # application.properties
   spring.task.execution.pool.core-size=4
   spring.task.execution.pool.max-size=8
   

   int availableCpus = (int) Math.min(
       Runtime.getRuntime().availableProcessors(), 
       Double.parseDouble(System.getenv("CPU_LIMIT"))
   );
   ExecutorService executor = Executors.newFixedThreadPool(availableCpus * 2);
   

public static int getContainerCpuLimit() {
  try (BufferedReader reader = new BufferedReader(
      new FileReader("/sys/fs/cgroup/cpu.max"))) {
    String line = reader.readLine();
    String[] parts = line.split(" ");
    long quota = Long.parseLong(parts[0]);
    long period = Long.parseLong(parts[1]);
    return (int) (quota / period); // Например, 1.5 → 1
  }
}

environment:
  JAVA_TOOL_OPTIONS: >-
    -XX:+UseContainerSupport
    -XX:MaxRAMPercentage=75.0
    -XX:+UseZGC
    -Djava.security.egd=file:/dev/./urandom

docker exec myapp jstat -gcutil 1 1000

# Стэк-трейс
docker exec myapp jstack 1 > thread_dump.txt

# Мониторинг GC
docker exec myapp jstat -gcutil 1 1000

# Heap-дамп
docker exec myapp jcmd 1 GC.heap_dump /tmp/heap.hprof

    debug-tools:
      image: openjdk:17
      volumes:
        - /var/run/docker.sock:/var/run/docker.sock
      command: ["jstack", "myapp"]
    

    RUN jlink \
        --add-modules jdk.jfr,jdk.management \
        --output /jlinked
    

environment:
  JAVA_TOOL_OPTIONS: >-
    -Dcom.sun.management.jmxremote.port=9090
    -Dcom.sun.management.jmxremote.rmi.port=9090
    -Dcom.sun.management.jmxremote.ssl=false
    -Dcom.sun.management.jmxremote.authenticate=false
    -Djava.rmi.server.hostname=myapp
ports:
  - "9090:9090"

  -Dcom.sun.management.jmxremote.rmi.port=9090
  

# Запуск записи
docker exec myapp jcmd 1 JFR.start name=recording duration=60s filename=/tmp/recording.jfr

# Экспорт метрик в Prometheus
RUN jcmd 1 JFR.configure stackdepth=128

   <dependency>
     <groupId>io.micrometer</groupId>
     <artifactId>micrometer-registry-prometheus</artifactId>
   </dependency>
   

   management.endpoints.web.exposure.include=prometheus
   

   services:
     app:
       ports:
         - "8080:8080"
     prometheus:
       image: prom/prometheus
       volumes:
         - ./prometheus.yml:/etc/prometheus/prometheus.yml
       ports:
         - "9090:9090"
   

   scrape_configs:
     - job_name: 'java'
       metrics_path: '/actuator/prometheus'
       static_configs:
         - targets: ['app:8080']
   

public class Task100925 {
    public static void main(String[] args) {
        int[] a = {1, 2, 3};
        int[] b = a;
        b[0] = 10;
        System.out.println(a[0]);
    }
}